FEATURE: Added basic GoodJob collectors (#280)

Author: AndersGM

README.md

@@ -21,6 +21,7 @@ To learn more see [Instrumenting Rails with Prometheus](https://samsaffron.com/a
   * [Puma metrics](#puma-metrics)
   * [Unicorn metrics](#unicorn-process-metrics)
   * [Resque metrics](#resque-metrics)
+  * [GoodJob metrics](#goodjob-metrics)
   * [Custom type collectors](#custom-type-collectors)
   * [Multi process mode with custom collector](#multi-process-mode-with-custom-collector)
   * [GraphQL support](#graphql-support)
@@ -627,6 +628,29 @@ PrometheusExporter::Instrumentation::Resque.start
 | Gauge | `resque_workers`        | Total number of Resque workers running |
 | Gauge | `resque_working`        | Total number of Resque workers working |
 
+### GoodJob metrics
+
+The metrics are generated from the database using the relevant scopes. To start monitoring your GoodJob
+installation, you'll need to start the instrumentation:
+
+```ruby
+# e.g. config/initializers/good_job.rb
+require 'prometheus_exporter/instrumentation'
+PrometheusExporter::Instrumentation::GoodJob.start
+```
+
+#### Metrics collected by GoodJob Instrumentation
+
+| Type  | Name                 | Description                             |
+| ---   |----------------------|-----------------------------------------|
+| Gauge | `good_job_scheduled` | Total number of scheduled GoodJob jobs. |
+| Gauge | `good_job_retried`   | Total number of retried GoodJob jobs.   |
+| Gauge | `good_job_queued`    | Total number of queued GoodJob jobs.    |
+| Gauge | `good_job_running`   | Total number of running GoodJob jobs.   |
+| Gauge | `good_job_finished`  | Total number of finished GoodJob jobs.  |
+| Gauge | `good_job_succeeded` | Total number of succeeded GoodJob jobs. |
+| Gauge | `good_job_discarded` | Total number of discarded GoodJob jobs  |
+
 ### Unicorn process metrics
 
 In order to gather metrics from unicorn processes, we use `rainbows`, which exposes `Rainbows::Linux.tcp_listener_stats` to gather information about active workers and queued requests. To start monitoring your unicorn processes, you'll need to know both the path to unicorn PID file and the listen address (`pid_file` and `listen` in your unicorn config file)

lib/prometheus_exporter/instrumentation/good_job.rb

@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+
+# collects stats from GoodJob
+module PrometheusExporter::Instrumentation
+  class GoodJob < PeriodicStats
+    def self.start(client: nil, frequency: 30)
+      good_job_collector = new
+      client ||= PrometheusExporter::Client.default
+
+      worker_loop do
+        client.send_json(good_job_collector.collect)
+      end
+
+      super
+    end
+
+    def collect
+      {
+        type: "good_job",
+        scheduled: ::GoodJob::Job.scheduled.size,
+        retried: ::GoodJob::Job.retried.size,
+        queued: ::GoodJob::Job.queued.size,
+        running: ::GoodJob::Job.running.size,
+        finished: ::GoodJob::Job.finished.size,
+        succeeded: ::GoodJob::Job.succeeded.size,
+        discarded: ::GoodJob::Job.discarded.size
+      }
+    end
+  end
+end

lib/prometheus_exporter/server.rb

@@ -19,3 +19,4 @@
 require_relative "server/active_record_collector"
 require_relative "server/shoryuken_collector"
 require_relative "server/resque_collector"
+require_relative "server/good_job_collector"

lib/prometheus_exporter/server/collector.rb

@@ -23,6 +23,7 @@ def initialize(json_serializer: nil)
       register_collector(ActiveRecordCollector.new)
       register_collector(ShoryukenCollector.new)
       register_collector(ResqueCollector.new)
+      register_collector(GoodJobCollector.new)
     end
 
     def register_collector(collector)

lib/prometheus_exporter/server/good_job_collector.rb

@@ -0,0 +1,52 @@
+# frozen_string_literal: true
+
+module PrometheusExporter::Server
+  class GoodJobCollector < TypeCollector
+    MAX_METRIC_AGE = 30
+    GOOD_JOB_GAUGES = {
+      scheduled: "Total number of scheduled GoodJob jobs.",
+      retried: "Total number of retried GoodJob jobs.",
+      queued: "Total number of queued GoodJob jobs.",
+      running: "Total number of running GoodJob jobs.",
+      finished: "Total number of finished GoodJob jobs.",
+      succeeded: "Total number of succeeded GoodJob jobs.",
+      discarded: "Total number of discarded GoodJob jobs."
+    }
+
+    def initialize
+      @good_job_metrics = MetricsContainer.new(ttl: MAX_METRIC_AGE)
+      @gauges = {}
+    end
+
+    def type
+      "good_job"
+    end
+
+    def metrics
+      return [] if good_job_metrics.length == 0
+
+      good_job_metrics.map do |metric|
+        labels = metric.fetch("custom_labels", {})
+
+        GOOD_JOB_GAUGES.map do |name, help|
+          value = metric[name.to_s]
+
+          if value
+            gauge = gauges[name] ||= PrometheusExporter::Metric::Gauge.new("good_job_#{name}", help)
+            gauge.observe(value, labels)
+          end
+        end
+      end
+
+      gauges.values
+    end
+
+    def collect(object)
+      @good_job_metrics << object
+    end
+
+    private
+
+    attr_reader :good_job_metrics, :gauges
+  end
+end

test/server/good_job_collector_test.rb

@@ -0,0 +1,78 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require 'prometheus_exporter/server'
+require 'prometheus_exporter/instrumentation'
+
+class PrometheusGoodJobCollectorTest < Minitest::Test
+  include CollectorHelper
+
+  def collector
+    @collector ||= PrometheusExporter::Server::GoodJobCollector.new
+  end
+
+  def test_collecting_metrics
+    collector.collect(
+      {
+        "scheduled" => 3,
+        "retried" => 4,
+        "queued" => 0,
+        "running" => 5,
+        "finished" => 100,
+        "succeeded" => 2000,
+        "discarded" => 9
+      }
+    )
+
+    metrics = collector.metrics
+
+    expected = [
+      "good_job_scheduled 3",
+      "good_job_retried 4",
+      "good_job_queued 0",
+      "good_job_running 5",
+      "good_job_finished 100",
+      "good_job_succeeded 2000",
+      "good_job_discarded 9"
+    ]
+    assert_equal expected, metrics.map(&:metric_text)
+  end
+
+  def test_collecting_metrics_with_custom_labels
+    collector.collect(
+      "type" => "good_job",
+      "scheduled" => 3,
+      "retried" => 4,
+      "queued" => 0,
+      "running" => 5,
+      "finished" => 100,
+      "succeeded" => 2000,
+      "discarded" => 9,
+      'custom_labels' => {
+        'hostname' => 'good_job_host'
+      }
+    )
+
+    metrics = collector.metrics
+
+    assert(metrics.first.metric_text.include?('good_job_scheduled{hostname="good_job_host"}'))
+  end
+
+  def test_metrics_expiration
+    data = {
+      "type" => "good_job",
+      "scheduled" => 3,
+      "retried" => 4,
+      "queued" => 0
+    }
+
+    stub_monotonic_clock(0) do
+      collector.collect(data)
+      assert_equal 3, collector.metrics.size
+    end
+
+    stub_monotonic_clock(max_metric_age + 1) do
+      assert_equal 0, collector.metrics.size
+    end
+  end
+end